This invention provides a novel structural unit that is derived from a glassy material which comprises glass microballoons. Glass structural units have been prepared in the prior art by sintering a mass of hollow glass particles to fuse the skins at their points of contact so that a structural unit is formed which is porous and not waterproof. These are disclosed in U.S. Pat. Nos. Re 25,564 and 3,458,332. The present invention is a closed pore, waterproof, substantially rigid material which has excellent insulating properties.
Cenospheres are cellulated glass microballoons or spherical, hollow glass particles which are a component of the fly ash obtained from the combustion of coal. They are described in detail by Raask, J. of the Institute of Fuel, pp. 339-344 (September, 1968) which is hereby incorporated by reference. The present invention provides a novel procedure for making a novel structural unit from cenospheres. This structural unit may be used as an insulating material for aerospace and other applications.
The novel closed-pore ceramic resists slag corrosion and gas erosion. It has high compressive strength and is readily machinable and can be fabricated into any desired size or shape using conventional techniques.